Hypothesis
by Hikareh
Summary: Tails needs to test something and Knuckles is the perfect person to help him.


_Hypothesis_

 **Notes:** This is just something I wrote really fast for a tumblr post a few weeks ago. Someone asked Katiemonz if Tails would experiment to see if Sonic is ticklish and I just ran with it. I would link to the post but fanfiction is suffering. **  
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_Forward!_

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So Tails has this hypothesis, but he also has self-preservation. He also has to be aware of scientific bias when conducting experiments, so he has to go about this the right way, or else his data will not be publishable.

(By all this, he means he just doesn't want to get kicked into next week.)

Knuckles, however, does not have such a strong sense of self-preservation (the gullibility cancels that out), and he won't know about the experiment as long as Tails convinces him the right way. It's perfect. He can already see it.

It's actually surprisingly easy to get Knuckles on board—possibly because he's not happy with Sonic for some asinine reason; typical of him, but Tails can't find it himself to care unless they actually start fighting. All he has to do is walk into the kitchen, put his hands on his hips, and say, "Hey, Knuckles, did you know that there's this theory that laughter while being tickled is a fear response?"

And Knuckles perks right up from where he's digging in the fridge (probably looking for grapes). He tries not to look terribly, impossibly fascinated by this new information, but he absolutely is. Tails can read him like a book. "Oh yeah?"

"Yeah totally. They say it's because the reaction comes from the part of the brain tied to panic."

"Oh _yeah_?"

Tails can practically see the little cogs turning in his head as he puts it together. All he needs is the last push. "Yeah," he repeats, "that's why ticklish spots are the weakest spots on the body. We laugh to try to appear submissive."

Knuckles is completely facing him now, smile wicked, and he closes the fridge with purposeful exactness. Then, he turns and heads right for Sonic, where he's sleeping on the couch. "Let's test this," he says (he actually says it!) as he passes by Tails, and it takes all of the fox's self-control to contain his glee.

Tails doesn't exactly get to see what happens immediately because Knuckles leans over the back of the couch to stab his fingers into Sonic's side, but Tails definitely hears the _yelp_. Knuckles, of course, takes this as a success, and he vaults over to continue his assault. Tails carefully stays ducked around the corner to watch from a safe distance.

"Dude, what the heck!" Sonic isn't happy, that much is clear even though he's laughing that strangled, panicked laugh he only uses when he can't control a situation. "Stop!"

Knuckles doesn't stop. In fact, he just increases his efforts, eliciting more and more wheezes from Sonic.

Unfortunately for Knuckles, Sonic has a fantastic presence of mind when under distress, and he eventually gets his feet under conscious control, plants them on Knuckles's chest, and kicks the last echidna on the planet right into the wall.

There's a crash upstairs as something falls, and what sounds like Knuckles strangling on his own esophagus. Sonic, unaffected by the fact that he may have just been the final extinction event for the echidna species, gets swiftly to his feet, quills raised in agitation. He looks two times bigger, which would have probably been really scary if he hadn't just lost control because of a _tickle_ attack.

Still, Tails's hypothesis has been proven true. When tickled, Sonic will react negatively, often with force, because his survival instincts—honed through years of near-death experiences—are too strong to ignore, even when faced with a friendly agent. It's all very fascinating and satisfying, but he can't help but feel bad for poor Knuckles.

Until, that is, Sonic pads toward him, levels a finger with his nose, and says " _you_ " with all the force of his being. It's with such power that Tails knows, immediately, that Sonic knows, and that _you_ is the most offensive curse he can muster right now.

Tails feels his hands rise to defuse the situation, but Sonic shakes his head and turns away. "No more science on me, Tails!" he calls as he opens the door to the outside world. "I'm not kidding!"

Then, he's gone, and Tails has to deal with Knuckles, still wheezing on the floor. But, it was worth it.

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 _Reviews are cherished._


End file.
